Method for strengthening metals



Oct. 4, 1966 B. LANGENECKER METHOD FOR STRENGTHENING METALS 4 Sheets-Sheet 1 Filed June 11, 1963 FIG.

E z. w 6955 55mm GLIDE STRAIN a FIG. 2.

INVENTOR. BERTWIN LANGENECKER ATTORNEY.

Oct. 4, 1966 B. LANGENECKER METHOD FOR STRENGTHENING METALS 4 Sheets-Sheet 2 Filed June 11, 1963 1/ d c 6 h m m to w.

R z. N 355 E35 GLIDE STRAIN a FIG. 3.

O O t 5 K R z. 6 mmwmkw 13 5w GLIDE STRAIN INVENTOR. BERTWIN LANGENECKER FIG. 4.

f A ATTORN EY.

4, 1966 B. LANGENECKER 3,276,918

METHOD FOR STRENGTHENING METALS Filed June 11, 1963 4 Sheets-Sheet 5 w 10 u) t LU E N m s B n: b

FG. 5. E

I 6 W G g 2 l- 4 E o u 2 U) 4 E U E (x no) PRESSURE AMPLITUDE, P, m din/6M i k B N 360 Q N g g 320 R 600 280 z fix AWITHOUT ULTRASONIC z 240 RADIATION n B=AFTER ULTRASONIC RADIATION w 200 U) 400 m Lu uJ a: s0- lm u) 200 A g I 60 (0 m to I i I I o oil 0 0.05 O.l0 0J5 GLIDE STRA|N,a GLlDE STRAIN FlG. 7. FIG. 6.

INVENTOR.

BERTWIN LANGENECKER XAZM ATTORN E Y.

Oct. 4, 1966 B. LANGENECKER METHOD FOR STRENGTHENING METALS Filed June 11, 1963 STRESS IN K /mm ALUMINUM 35 WATT /cm STRAIN, soumo (lo ev/cm FIG. 8A.

SOUND PRESSURE. AMPLITUDE (a /6M STRESS 'lN Kg/mm 4 SheetsSheet 4 G ALUMINUM GOO'C STRAIN, "4,

HEAT (IO e M FIG. 88.

r-'\ t I l I 2 s 4 5 mead; IO IO l0 l0 l0 INTENSITY (WATT /cm FIG. 9.

INVENTOR. BERTWIN LANGENECKER f AK 61% ATTORNEY.

United States Patent 3,276,918 METHOD FOR STRENGTHENING METALS Bertwin Langenecker, China Lake, Calif., assignor to the United States of America as represented by the Secretary of the Navy Filed June 11, 1963, Ser. No. 287,157 Claims. (Cl. 148-129) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates to improvements in treatment of metals and more particularly to an improved method of strengthening metals by passing sound waves through a solid or liquid phase metal body to effect a high strength network of crystal lattice defects, commonly referred to as dislocations or grain boundaries and thereby providing for a substantial increase in the shear stress and static yield strength of the thus treated body.

In the field of metallurgy, many techniques involving the application of sound waves are well known. However, the known metal treating techniques in which sound waves are employed as tools for solving problems arising in metal physics are ordinarily found in areas of measuring elastic and optical constants, and damping attenuation.

It has been suggested by Blaha and Langenecker in Dehnung von Zink-Kristallen unter Ultraschalleinwirking, Naturwissenschaften, vol. 42, page 556, 1955, that sound wave effects on lattice dislocations may be utilized in research on plasticity of crystals. However, the results obtained by Blaha and Langenecker tended to show that a reduction in static yield strength of a zinc body was obtainable when using sound fields having pressure amplitudes below 10' dyn./cm. (dynes per square centimeter). The aforementioned results failed to indicate that the yield stress could be increased when using sound fields having pressure amplitudes greater than 10' dyn./ cm.

Hence, it is to be understood that the heretofore known approaches to work-hardening, or raising the yield point and static yield strength of solid-phase metals, have been confined .to approaches utilizing conventional techniques for strengthening metals, which techniques ordinarily employ thermal energy and/or pressure (stress) treatments, as well as various modifications of the basic procedural steps utilized in the conventional techniques.

Certain disadvantages are inherent in the aforementioned techniques, for example, when fabricated or machined metal parts are to be strengthened so as to raise their yield point, a substantial period of time is necessary to oven treat the parts, and cool and/ or age the oven treated metallic parts at a given rate to attain desired physical characteristics. Furthermore, when the techniques utilized for work-hardening metal involve straining a metal body beyond its elastic limit to effect a work-hardening increase in the static yield strength thereof, permanent deformation of the body occurs. Thus such techniques are not considered to be satisfactory for treating fabricated parts.

Advances in conventional techniques utilized for workhardening a metal body, which permits the metallic body to retain its original size and shape, have been substantially stabilized. At present the yield point and static yield strength of metals can be increased by only several percentage points, even under optimal conditions.

Each metal crystal has within its lattice a large number of dislocations in the form of voids created through a disorderly arrangement of atoms within the lattice. :It has been fairly well established that a dislocation forms a center about which there is a locking concentration of confining dissolved atoms. A well-known theory exists to the effect that when sufl'icient stress is applied to a metal 3,276,918 Patented Oct. 4, 1966 crystal, certain of the dislocations are caused to escape the confining influence of the dissolved atoms and migration of the dislocations is effected for accommodating plastic deformation. :The movements of dislocations, and therefore plastic deformation, is made easier through a conventional input of thermal energy, because the atoms concerned in the process possess energy of thermal agitation and are therefore more likely to have sufficient energy to permit an occurrence of dislocation migration.

Recent theories concerning work-hardening mechanisms indicate that work-hardening results from a reduction in the mean free path of migrating dislocations, which reduction is caused by a continuous formation of obstacles dur ing glide to form locked vacancy rings so disposed as to have their Burgess vectors directed out of the basal plane. The obstacle formation is implemented, during workhardening, through an intersection of migrating dislocations with immobile dislocations, regardless of how the force which drives the dislocations is originated.

in has been suggested that thermal energy is absorbed homogeneously in a metallic body, whereas energy of sound concentrates at crystal lattice defects, such as dislocations, grain boundaries and the like, and is there absorbed. The passage of sound Waves of sufficient intensity through a metallic body will apparently first oscillate and then lift the absorbing dislocations from their equilibrium positions. If the body is simultaneously placed under a stress, within the dictates of the elastic limits of the body, the dislocations will become mobile and work-hardening similar to that achieved through the aforementioned techniques will occur. Furthermore, even in the absence of stress, sound waves having still a higher order of amplitude may have an effect similar to that described for a body under strain when treated with lower macrosound amplitudes.

While it is quite reasonable to ascribe work-hardening by sound waves to similar dislocation mechanisms as found for high temperature deformation, the comparison of the energies transferred to the crystal thermally and by sonic irradiation evidence remarkable differences. For instance, when utilizing a low ultrasonic radiation field at room temperature, with intensity pressure amplitude of less than 10 dynes per centimeter squared, the sound energy transferred to the crystal is in the order of 10 electron volts per centimeter cubed. In comparison with this, a coincident stress-strain curve obtained at elevated temperatures, in the absence of irradiation, requires a thermal energy input of about l0 electron volts per centimeter cubed, thus indicating that a process involving thermal energy input necessitates a significantly greater energy transfer.

Heretofore, as hereinbefore mentioned, investigations on zinc bodies have been carried out in sound fields having pressure amplitudes lower than 10' dyn./cm. and have failed to indicate that a significant increase in tensile strength may be obtained through the use of sound energy, since amplitudes of such order merely serve to temporarily lower the yield point which will subsequently return only to an original. value. However, in accordance with the present discovery it has been found that where the pressure amplitude is increased to a value greater than 2.5 l0 dynes per square centimeter, the shear stress of the zinc body will first be reduced during sonic application, but after irradiation will be increased to a value substantially greater than the original value.

The present invention makes effective use of the discovered capacity of macrosonic Waves to free and mobilize crystal lattice dislocations to effect work-hardening without concurrent deformation.

Furthermore, according to the present discovery it has been found that ultrasonic radiation causes an increase in work-hardening, D1, of an order of grams per square millimeter within a glide strain of the order 3 of 0.03; Such result is similar to work-hardening effects attained through straining a given body beyond its elastic limits in the absence of an ultrasonic radiation field and at glide strains higher by at least one order of magnitude.

Therefore, energy of sound may be utilized to achieve metal work-hardening with many attendant advantages, such as affording a saving in time necessary to treat the metals, and a substantial saving in energy required in achieving a substantial increase in work-hardening characteristics, Additionally, certain other very important advantages are present. For example, as annealing ordinarily takes place simultaneously with work-hardening, there is a reduction in the amount of effective workhardening caused by the mechanisms of annealing, or recovery. Annealing and recovery, however, depend on temperature and are not influenced by sound waves. In other words, obstacle formation is less hindered in case of ultrasonic radiation than in the aforementioned conventional techniques thus permitting a metal body to be work-hardened at relatively low temperatures Without deformation.

The purpose of the present invention is to provide a new technique for increasing the stress yield point and static yield strength of metals up to, in some instances, 500 percent above an original value, by rearranging the atomic lattice defects within a solid-phase metal body through the application of sound waves having pressures of high amplitude.

An object of the present invention is to provide a method of work-hardening metals which utilizes sound waves to expeditiously work-harden solid-phase metal bodies in a geometrical non-deforming manner.

Another object is to provide a method utilizing sound waves to rearrange areas of dislocations present as lattice defects within a given metal body.

A further object is to provide a method for increasing the yield stress and static yield strength of metal bodies through application thereto of ultrasonic radiation.

Still a further object of the present invention, as applied to the treatment of metals in their pure or alloyed state, is to provide a method for activating atomic lattice dislocations and causing them to become mobile and migrate to form locked vacancy rings through the application of ultrasonic wave pressure to the grain boundaries thereof so that the atomic lattice of the body may be properly rearranged to thus impose work-hardening physical characteristics on the body.

Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings wherein:

FIG. 1 is a diagrammatic view illustrating a device of type which may .be utilized in performing the method of the instant invention;

FIGPZ is. a graph having a plurality of stress-strain curves illustrating the effects of repeated high-amplitude ultrasonic radiation on stress-strain curves of a zinc body;

FIG. 3 is a graph having a plurality of stress-strain curves illustrating the effect of continuous high-amplitude ultrasonic radiation on a stress-strain curve of a zinc crystal;

FIG. 4 illustrates a series of stress-strain curves for a zinc crystal, being formed through periodic unloading with high-amplitude ultrasonic radiation occurring during unloaded periods;

FIG. Sis a graph showing a stress-strain curve illustrating the relationship between resulting work-hardening characteristics of a zinc body and the ultrasonic amplitudes which are utilized to imposed the work-hardening characteristic on the body;

FIG. 6 is a graph showing the difference. in yield points before and after ultrasonic radiation on a specific body;

FIG. 7 is a graph providing a pair of stress-strain curves for comparative illustration of results obtained 4 through straining and ultrasonic irradiation of an aluminum body;

FIGS. 8A and 8B comprise a pair of stress-strain curves illustrating the effects of sound waves at various intensities as compared with effects caused through heating the body; and

FIG. 9 is a chart denoting a relationship between sound field intensity and sound pressure amplitude as they occur in different metals.

Turning now to the drawings, there is shown in FIG. 1 a device 10 illustrating a type of device which may be utilized in performing the method of the present invention. The specific device utilized may be varied as desired by one skilled in the art, and the disclosed device is intended to provide no more'than a mere representation of a class of devices which may, if desired be employed to perform the method of the present invention.

The device 10,, utilized for treating a specimen or body 11, is provided with a motor-driven micrometer 12 having a load cell weighing system 13 for detecting the imposed tensile load. A body holder, 14 is provided and attached to one end of the body 11 for connecting the body with the load cell 13. A fixed 25 kc. (kilocycle) ultrasonic transducer 15, capable of producing sound field having pressure amplitudes up to about 10 dyn./crn. is secured to the opposite end of the body 11 for generating and providing a high-amplitude ultrasonic radiation field within a chamber 16, in which the body 11 is so disposed that it may be subjected to the transducer generated field and where desired, concurrently with an imposition of a strain.

In order to more fully describe the present invention, reference is made particularly to results which may be attained at room temperature when utilizing zinc bodies, or crystals, 10 to 20 mm. (millimeters) long and 0.6 to 1.2 mm. in diameter. The crystals utilized, for the purpose of the illustration, may be grown from melts, such as cominco 59 grade metal. The crystals utilized may be grown by the Czochral-ski method, which is more fully described by LCzochralski in Production of Crystals by Drawing from the Melt, Zeilschrift fur Physikalische Chemie, vol. 92, page 219 (1917).

The upper end of the body, or specimen 11, as shown in FIG. 1, is fixed to the load cell 13 through the holder 14 and hence to the micrometer 12, while the lower end thereof is fixed through any suitable means to the ultrasonic transducer 15. If the zinc body 11 is exposed to the ultrasonic irradition effects of the transducer 15,, functioning with pressure amplitudes of less than 10"dynes per square cm. at 25 kc. during straining, stress within the body is reduced markedly as soon as sound waves are caused to pass through the body, however, when the sound filed is removed, the shear stress will return only to its original value. A larger reduction in the shear stress will occur as the pressure amplitude is increased through values up to 2.5)(10 dynes per square cm. with no permanent change occurring in the stress-strain curve, i.e., the stress value will return only to its original value when the body is removed from the field of radiation; The present invention resides in the discovery that it is possible to work-harden metals by utilizing intense sound waves in an ultrasonic field of an order greater than 2.5 x10 dynes per square centimeter when applied to a metal body in a device of the type hereinbefore mentioned. It has been found that the elastic limit is first substantially .reduced, but upon further straining, without sound, the shear stress necessary for plastic deformation will begin to increase and continues to so increase during the stressing. After the field of radiation is removed, the yield point undergoes a sharp and immediate increase well above the original value.

To more clearly illustrate this phenomena, attention is directed particularly to FIG. 2. At t (original stress value) a body is subjected to a glide strain of 2X10 per sec., and at points indicated a, e, i, and m, an intense ultrasonic field, having a pressure amplitude greater than 2.5 X10 dynes per square centimeter is applied to the zinc specimen, through periods indicated by the dotted lines: a, b, c; e, f, g; i, j, k; and m, n, 0. In each instance, the yield point is initially reduced to a substantially reduced stress point, designated b, j, and n, and upon a continued application of stress and ultrasonic radiation the shear stress value is increased to points c, g, k, and o, whereupon, when the sound field is removed and the shear stress yield point increases to points designated by points d, h, e, and p. For example, irradiation of the specimen may begin at the point designated a and extend over a period in which the glide strain is increased by 0.01 of its value at point a to point c, the ultrasonic generator may then be switched off, thereupon the shear stress yield point t will undergo a further increase to point d, which comprises a shear stress value much higher than the original value t at point a. If the same procedure is now repeated in the regions e-h, i-l, and m-p, the bodys work-hardening coeflicient 0, (where 9=dt/da, and a is given glide strain value) will decrease from one irradiated region to the next in the direction of increasing glide strain. Simultaneously, the difference in tensile strengths before and after irradition decreases. By comparing the stress 1 required for plastic deformation at points I and p, it will be understood that it is possible to attain saturation of physical work-hardening characteristics, since further irradiation and straining does not significantly increase the yield point value.

It is to be particularly noted that where found desirable, a continuous irradiation and straining of the specimen may be utilized to achieve a similar saturation effect. Results of continuous irradiation and straining is clearly illustrated in FIG. 3. As shown in FIG. 3, t indicates an original yield point or shear stress value at which deformation will occur. Now, if strain is applied to the body and irradiated from point a through point 0, the elastic limit initially and substantially decreases during radiation, but subsequently increases to a value far above its original value t The approach of the work-hardening coefficient 9 to zero is indicated by the dotted line which is also coincident with a strain value, 0.03 of the strain imposed at the beginning of the irradiation period. At point 0, the ultrasonic field is removed whereupon the yield point for the shear stress I increases immediately to d, which indicates a yield point value similar to that indicated at point h of FIG. 2; i.e., the point at which workhardening saturation is achieved.

If the irradiated specimen is unloaded after irradiation and is subsequently restrained, without further irradiation and after a substantial lapse of time, the yield point value approached will be approximately that of the saturated state as indicated at g, thus indicating that the yield point I thus attained may be considered to be substantially permanent. For example, point f, FIG. 3, represents a point at which a specimen was substantially unloaded, and aged for fourteen hours, and then restrained Without further irradiation. The stress necessary to cause the body to deform upon restraining, now approaches the point indicated g, which is slightly lower than e, the point at which the specimen was unloaded, but considerably above a, the original stress yield point t Similar results may be obtained by irradiating the specimen in an unloaded state, for example, the stress-strain curves of FIG. 4 serve to illustrate the efiects of sequential irradiation on a specimen in its unloaded state. The stress values at d, g and 1', may be obtained by straining without irradiation to determine the increase in the work-hardening of the body due to the effects of the applied ultrasonic irradiation applied at points b, e, and h.

Saturation is indicated at point j when the amplitude of the field is in the order of 4.5 x10 dyn./cm. Points l, m and 0 indicate the saturation eifect attained when the sound pressure amplitude of the radiation field is raised to a value of x 10' dynes per square centimeters. When Working with unloaded specimens, time of irradiation becomes important. For example, it has been found that a two minute irradiation period, for a zinc crystal, is required to attain a saturation point.

Amplitudes greater than 5.5)(10 dynes per square centimeter tend to plastically deform single zinc crystals of the type hereinbefore mentioned. In polycrystalline metals, sudden fracture will occur, usually along grain boundaries, when the amplitude of the pressure applied is extreme. Hence, it is to be understood that the pressure amplitude utilized must be matched to the strength of the particular metal being treated in such a manner as to ensure that an amplitude of the sound utilized is always of such an order as to preclude a plastic state for the metal from being attained to thereby avoid plastic deformation.

Work-hardening of metals, while not significantly dependent on frequency, is directly dependent upon pressure amplitude of the sound waves utilized for causing migration of dislocations within the lattice. A stresspressure amplitude curve, FIG. 5, clearly illustrates the relationship between pressure amplitude and work-hardening increase Dt, for Zinc crystals. Point P FIG. 5, indicates the pressure amplitude of the irradiation field at which Dt is initiated, and P indicates the point at which saturation occurs. Any further increase in the pressure amplitude of the field of radiation will fail to significantly raise the yield point beyond the yield stress valve 1. However, at saturation the yield point may comprise a point several hundred percentage points above the original yield stress value t For example, turning now to FIG. 6, a curve indicated A is obtained upon stressing an unirradiated zinc specimen, while after irradiation a curve indicated B is obtained, thus indicating an increase, Dr, of several hundred percentage points.

While the examples have been devoted primarily to single zinc crystals, it is to be clearly understood that the method herein disclosed is also readily applicable to various other metals. For example, the stress-strain curves, as shown in FIG. 7, indicate the results attained when straining an aluminum crystal. The solid line, designated A, indicates a stress-strain curve for an unirradiated aluminum crystal, while the dotted line curve B is used to illustrated the stress-strain curve for an irradiated aluminum crystal. Therefore, it is to be understood thatit is entirely feasible to significantly raise the yield point of an aluminum crystal utilizing the aforedescribed work-hardening technique. Other metals such as beryllium, stainless steel tungsten and low carbon steels have been treated, using the technique of the presenlt invention and have met with exceptionally good resu ts.

In order to treat metals other than zinc, the technique utilized in treating zinc crystals is employed as a fundamental technique to achieve a work-hardening effect in a similar manner. However, specific values utilized for treating the various metals may necessarily vary from metal to metal. Since the efficiency of the aforedescribed sound treating technique depends largely on the extent to which the yield points is first lowered, before an increase thereof occurs, it is necessary that the irradiation be so controlled as to prevent plastic deformation from being achieved.

As hereinbefore mentioned, it is possible to effect dislocation, or grain boundary, migration in the absence of non-acoustic strain, provided that the ultrasonic amplitude is sutficient. This eifect is more clearly shown in FIGS. 8A and 8B, wherein a plurality of stress-strain curves indicate comparative results obtained utilizing an aluminum crystal. It is to be noted the stress-strain curves of FIG. 8A were obtained at room temperature during an application of sound at various intensities and at 20 kc. When an intensity of about 50 watts/cm. is applied, the resulting stress-strain curve hardly rises above zero. In other words the metal may be caused to undergo plastic deformation at room temperature without apparent stress. The curve obtained at 18 C. (centigrade) during irradiation at 50 watts/cm. corresponds closely to the known curve for yielding of aluminum at about 600 C., FIG. 8B, when no appreciable sound is applied. A comparison of the curves of FIGS 8A and 8B thusindicates that sound reduces the shear stress necessary for plastic deformation with increasing amplitude in a manner similar to that obtained when heat is applied with increasing temperature.

In order to more clearly understand the efiect of sound waves on various metal bodies, it must be understood that sound creates certain stresses, which may be better illustrated through the utilization of the basic differential Equation 1 for the propagation of an elastic disturbance, i.e.:

Where denotes displacement of a particle from its equilibrium position at a distance X; T is the time of irradiation; C is the sound velocity.

A second Equation 2 comprises a particular solution where A is the amplitude of oscillation and w the angular frequency of the sound waves applied:

(2) =A sin 451 -6) After differentiating twice with respect to T a third equation is obtained:

which represents acceleration of particules due to pressure gradient, dp/dx. Hence, a fourth equation may be Written, keeping in mind the equation of motion according wherein p denotes density of the body being treated.

Finally, integration of Equation 4 with respect to T results in Equation 5 z ACOUSTIC STRESSES I AND 1)" AT 50 WATTS/CM AND YIELD STRESSES P p t dyne/em 2 dyne/crn. dyne/cm.

It is to be noted that for the various metals, as shown in the above chart, P extends from 5.3 to 10x10 dynes/ cmfi, and the radiation pressure 17* lies between 0.4 and 1.5 X 10 dynes/cm. while the shear stresses t necessary to effect plastic deformation varies between 1X10 and 1 10 dynes/cmfi, depending on certain determinable factors, such as the specific metal being treated, its structure, crystallographic orientation factors, and the like.

As has hereinabove pointed out, in order to effectively utilize the work-hardening effects of macrosonic waves, it is necessary that plastic deformation be avoided, hence, the particular metal body being treated must be subjected to an ultrasonic field'which is sufficient to activate dislocations or grain boundaries, but which is insufiicientjto cause the body to undergo physical distortion. Therefore, it

is convenient to determine the relationship between field intensity and the sound pressure amplitude with respect to the specific metals being treated. For this purpose a chart, such as the chart of FIG. 9, may be utilized for specific metals to illustrate the relationship between the field intensity in watts/cm. (or decibels, db) and the sound pressure amplitude P in dynes/cm. as they occur in dilferent metals. For example, the yield point t of Al (aluminum), Be (beryllium), Fe (iron) and W (tungsten) corresponds to sound pressure levels greater than 10 dynes/cmf and thus require sound intensities gerater than watts/cm. at a temperature of 295 K. (Kelvin scale).

In accordance with the foregoing, it is to be understood that the yield stress and corresponding field intensity for most metals may be determined so that they may be treated by utilizing sound waves of determinable amplitude to effect a work-hardening thereof in accordance with the hereinbefore described method.

While the above-described method may preferentially be performed at ambient room temperature, itis to be understood similar results may be attained whenthe temperature of the particular specimen being treated is elevated through a range extending up to the specific melting point of the particular metal being treated. Therefore, it has been found that temperature is not a restricting factor when the above-described ultrasonic work-hardening technique is utilized for treating metal bodies.

In summary, it is pointed out that the ultrasonic field intensity necessary for activating lattice defects for a specific metal body, Whether under mechanical stress or in the absence thereof, may be determined according to the foregoing differential equation. If the body is subjected to a radiation field of sufiicient-intensity and, if desired, mechanical stress, dislocation migration will be caused to occur so that the yield point of the metal will first be reduced, for instance to zero yield point and subsequently rise to a point well above its original value this imparting thereto work-hardening characteristics. similar to those imparted when heat and/or stress is applied to a metal.

body. However, it is to be understood that physical distortion does not accompany ultrasonic work-hardening and the results achieved may be with a substantial saving in energy input and time required to perform the treating process, as compared with the hereinbefore mentioned conventional techniques.

In accordance with the hereinabove disclosure, it is to be understood that the present invention provides a method for expeditiously work-hardening metals through the use of ultrasonic waves, or sound waves having high pressure amplitudes, for activating and causing migration of atomic lattice dislocations to provide a work-hardened specimen in an undeformed state.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. The method of Work-hardening treating a solidphase metallic body comprising the steps of exposing the body to a field of ultrasonic radiation having a pressure amplitude suflicient to impose a mobile state on atomic lattice dislocations present within the body;

removing the field of ultrasonic radiation; and

aging the body for a period sufiicient to establish a relative stable state for said dislocations.

2. The method of claim 1 further including the step of:

imposing a glide strain on said body while it is exposed to said field of radiation.

3. The method of claim 2 wherein the glide strain constitutes a fraction of the yield point of the body.

4. In a method of work-hardening a metallic body comprising the step of:

subjecting the body to a field of ultrasonic radiation having a pressure amplitude sufi'icient to activate lattice dislocations and cause a migration thereof.

5. The method of claim 3 wherein the pressure amplitude of the radiation of said field is sufiicient to activate said dislocation.

6. The method of claim 3 wherein a glide strain is simultaneously imposed on said body during subjection of said body to said field of radiation.

7. The method as defined in claim 6 further characterized in that the method steps are performed at ambient room temperature.

8. In a method of treating a solid-phase metallic body for effecting a desired work-hardening characteristic, while maintaining the body in a geometrically undeformed state, the step of:

subjecting the body to a field of ultrasonic waves of determinable amplitude to effect migration and rearrangement of atomic lattice dislocation.

9. The method as defined in claim '8, further comprising the step of:

simultaneously subjecting the body to a continuous strain within the elastic limits of the body. 10. A method for increasing the shear stress value of a given metallic body while maintaining the body in an undeformed state, comprising steps of:

providing a field of sound waves having a pressure amplitude of a value necessary for activating atomic lattice dislocations within the given body;

subjecting the body to -a strain below its elastic limits;

and

simultaneously subjecting the body to said field for a determinable period, whereby the atomic lattice dislocations are caused to migrate outwardly and to form locked lattice defects to thus provide work-hardening characteristics within the body.

OTHER REFERENCES Vibration Treatment of Metals, Seemann et al., Journal of the Acoustical Society of America, vol. 29, No. 6,

June 1957, pp. 698-701.

DAVID L. RECK, Primary Examiner.

H. F. SAITO, Assistant Examiner. 

1. THE METHOD OF WORK-HARDENING TREATING A SOLIDPHASE METALLIC BODY COMPRISING THE STEPS OF: EXPOSING THE BODY TO A FIELD OF ULTRASONIC RADIATION HAVING A PRESSURRE AMPLITTUDE SUFFICIENT TO IMPOSE A MOLBILE STATE ON ATOMIC LATTICE DISLOCATIONS PRESENT WITHIN THE BODY; 